21420212220 has 288 divisors, whose sum is σ = 73146318336. Its totient is φ = 5029516800.

The previous prime is 21420212183. The next prime is 21420212221. The reversal of 21420212220 is 2221202412.

21420212220 is a `hidden beast` number, since 2 + 1 + 420 + 21 + 2 + 220 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21420212193 and 21420212202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420212221) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 8090937 + ... + 8093583.

It is an arithmetic number, because the mean of its divisors is an integer number (253980272).

Almost surely, 2^21420212220 is an apocalyptic number.

21420212220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21420212220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36573159168).

21420212220 is an abundant number, since it is smaller than the sum of its proper divisors (51726106116).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21420212220 is a wasteful number, since it uses less digits than its factorization.

21420212220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2801 (or 2796 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

Adding to 21420212220 its reverse (2221202412), we get a palindrome (23641414632).

The spelling of 21420212220 in words is "twenty-one billion, four hundred twenty million, two hundred twelve thousand, two hundred twenty".